Left-handed and right-handed people view the world differently, scientists have
shown.

Tussentitel: Not only our language function, but even the way we see the
world can depend on our handedness. Professor Glyn Humphreys

Psychologists found they use opposite sides of their brains when looking at,
and making sense of, an image.
It is already known that handedness is associated with
differences in the way we make sense of language, and possibly in spatial
orientation.
Details of the study, by the University of Birmingham, are
published in Nature Neuroscience.
The researchers showed right-handed people use the right
hemisphere of their brain to focus on the whole of an image - for example a
forest.
But when it comes to focusing on the detail within an image -
for instance individual trees in a forest - then they use their left hemisphere.
For left-handers the opposite is true.
The researchers used a technique called Transcranial Magnetic Stimulation (TMS)
which momentarily disrupts brain activity.
The researchers applied TMS over either the left or right
parietal lobe at the back of the brain while volunteers concentrated on the
details of a visual stimulus.
Stimulation of the left side of the brain made it harder for
right-handers to attend to detail, whilst stimulation of the right side had this
effect on left-handers.
Professor Glyn Humphreys from the University's School of
Psychology said: "In right-handed people the right hemisphere sees the whole
picture, whereas the left hemisphere attends to the details.
"However, we have found that in left-handed people, this is
completely reversed.
"Not only our language function, but even the way we see the
world can depend on our handedness."
Professor Humphreys told the BBC News website the findings
suggested that brain damage would affect left and right-handers ability to make
sense of detail in different ways. ...

Left-handed people can think quicker when carrying out tasks such as playing
computer games or playing sport, say Australian researchers.

Tussentitel: This seems to go with evidence that left-handers use both sides
of the brain for language. Dr Steve Williams

Connections between the left and right hand sides or hemispheres of the brain
are faster in left-handed people, a study in Neuropsychology shows.
The fast transfer of information in the brain makes
left-handers more efficient when dealing with multiple stimuli.
Experts said left-handers tended to use both sides of the
brain more easily.
Study leader Dr Nick Cherbuin from the Australian National
University measured transfer time between the two sides of the brain by
measuring reaction times to white dots flashed to the left and right of a fixed
cross.
He then compared this with how good participants were at
carrying out a task to spot matching letters in the left and right visual fields,
which would require them to use both sides of the brain at the same time.
Tests in 80 right-handed volunteers showed there was a strong
correlation between how quickly information was transferred across the left and
right hemispheres and how quickly people spotted matching letters.
But when the tests were repeated in 20 left-handed volunteers,
the researchers found that the more left handed people were the better they were
at processing information across the two sides of the brain.
Extreme left-handed individuals were 43 milliseconds faster at
spotting matching letters across the right and left visual fields than
right-handed people.

More efficient
Dr Cherbuin, research fellow at the University concluded: "These findings
confirm our prediction of increasing efficiency of hemispheric interactions with
increasing left-handedness."
But he added that it wasn't a clear-cut pattern as there were
subtle differences between strongly and mildly left-handed or right-handed
individuals.
Dr Cherbuin explained that people tended to use both
hemispheres for tasks which are very fast or very hard and which require
interpretation of a lot of information, such as computer games or driving in
heavy traffic or playing sport.

Chartered psychologist, Dr Steve Williams said left-handed
people tended to be better at using both sides of the brain.
"It's certainly very interesting. It's always been said that
left-handers are different from right-handers in that they are less consistent
with their left-handedness.
"This seems to go with evidence that left-handers use both
sides of the brain for language - that they are more bicerebral. They get faster
at it because they're having to use both sides of the brain more."
"In football, being able to shoot with either foot is a huge
asset (each foot like each hand is under opposite-side control) and I've heard
that left-handers tend to have better backhands in tennis," he added.

The Right Brain vs Left Brain test ... do you see the dancer turning clockwise
or anti-clockwise?
If clockwise, then you use more of the right side of the
brain and vice versa.
Most of us would see the dancer turning anti-clockwise though
you can try to focus and change the direction; see if you can do it.